Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Niskin Bottle

The Niskin bottle is a device used by oceanographers to collect subsurface seawater samples. It is a plastic bottle with caps and rubber seals at each end and is deployed with the caps held open, allowing free-flushing of the bottle as it moves through the water column.

Standard Niskin

The standard version of the bottle includes a plastic-coated metal spring or elastic cord running through the interior of the bottle that joins the two caps, and the caps are held open against the spring by plastic lanyards. When the bottle reaches the desired depth the lanyards are released by a pressure-actuated switch, command signal or messenger weight and the caps are forced shut and sealed, trapping the seawater sample.

Lever Action Niskin

The Lever Action Niskin Bottle differs from the standard version, in that the caps are held open during deployment by externally mounted stainless steel springs rather than an internal spring or cord. Lever Action Niskins are recommended for applications where a completely clear sample chamber is critical or for use in deep cold water.

Clean Sampling

A modified version of the standard Niskin bottle has been developed for clean sampling. This is teflon-coated and uses a latex cord to close the caps rather than a metal spring. The clean version of the Levered Action Niskin bottle is also teflon-coated and uses epoxy covered springs in place of the stainless steel springs. These bottles are specifically designed to minimise metal contamination when sampling trace metals.

Deployment

Bottles may be deployed singly clamped to a wire or in groups of up to 48 on a rosette. Standard bottles have a capacity between 1.7 and 30 L, while Lever Action bottles have a capacity between 1.7 and 12 L. Reversing thermometers may be attached to a spring-loaded disk that rotates through 180° on bottle closure.

PD10_10 dissolved nutrient data series measured by DEOS

Originator's Data Processing

Sampling Strategy

Samples for nutrient analyses were collected by the Department of Earth and Ocean Sciences, Liverpool University (DEOS) on a National Oceanography Centre, Liverpool (NOC) Oceans 2025 SO11 Coastal Observatory cruise (number 68) in Liverpool Bay and the Eastern Irish Sea. The cruise ran from 28 - 30 April 2010.

Single samples were collected near-surface and near-bed from water bottle rosette sampling systems mounted on the lowered CTD during 27 CTD casts carried out at stations throughout Liverpool Bay and the Eastern Irish Sea. Additionally, samples were taken from 22 casts at Site 1 over a 25 hour tidal cycle. Near-surface and near-bed samples were taken during the first and last casts of the tidal cycle, with single near-surface samples being taken during all other tidal cycle casts at Site 1.

The nutrient samples were collected directly from the rosette bottles into acid-washed, deionised water rinsed 125 ml high density polyethylene (HDPE) screw cap bottles. The HDPE bottles were rinsed 3 times with sample water and then filled with approximately 100 ml of sample. The bottles were then capped and labelled.

Data Processing

The samples were placed in a -20 °C freezer and frozen upright. The samples were transported frozen to Liverpool University for analysis. Prior to analysis, samples were defrosted in the dark and all analyses were performed within 1 week of sample collection. Analysis was carried out by splitting each single sample into triplicate sub-samples and analysing these using a Quaatro AQ2 Autoanalyzer 3 (Seal Analytical, 2006).

References

Processing Undertaken by BODC

The data were supplied to BODC as an Excel spreadsheet. This was converted to an ASCII format file for loading into the BODC archive. The variables supplied by the Data Originator were mapped to BODC parameter vocabularies as follows:

The data were loaded into the database by matching the sample's station identifier and depth with the information already held in the database for this cruise. Records for this cruise indicated that all near-surface samples were taken from either rosette bottles 5, 9, 10 or 12 depending on cast. The near-bed samples were taken from rosette bottles 2 or 3 depending on cast.

Data Quality Report

Nitrate + Nitrite

Quoted values for the near-surface and near-bed samples taken during cast CAST055, and for the near-surface samples taken during casts CAST054, CAST063, CAST074 and CAST075 have all been flagged. This flagging indicates the actual concentrations were below the limit of detection of the auto-analyzer. The detection limit is the quoted value (0.1 µmol l -1 ).

Silicate

Quoted values of silicate concentration have been flagged for the following samples: for the near-surface and near-bed samples taken during casts CAST060, CAST069 and CAST076; for the near-surface samples taken during casts CAST053, CAST061, CAST068, CAST070, CAST074 and CAST075; and for the near-bed samples taken during casts CAST004 and CAST078. This flagging indicates the actual concentrations were below the limit of detection of the auto-analyzer. The detection limit is the quoted value (0.5 µmol l -1 ).

Nitrite

Quoted values of nitrite concentration for the near-surface and near-bed samples taken during casts CAST064 and CAST075 and for the near-surface samples taken during casts CAST063 and CAST074 have all been flagged. his flagging indicates the actual concentrations were below the limit of detection of the auto-analyzer. The detection limit is the quoted value (0.1 µmol l -1 ).

Sustained, systematic observations of the ocean and continental shelf seas at appropriate time and space scales allied to numerical models are key to understanding and prediction. In shelf seas these observations address issues as fundamental as 'what is the capacity of shelf seas to absorb change?' encompassing the impacts of climate change, biological productivity and diversity, sustainable management, pollution and public health, safety at sea and extreme events. Advancing understanding of coastal processes to use and manage these resources better is challenging; important controlling processes occur over a broad range of spatial and temporal scales which cannot be simultaneously studied solely with satellite or ship-based platforms.

Considerable effort has been spent by the Proudman Oceangraphic Laboratory (POL) in the years 2001 - 2006 in setting up an integrated observational and now-cast modelling system in Liverpool Bay (see Figure), with the recent POL review stating the observatory was seen as a leader in its field and a unique 'selling' point of the laboratory. Cost benefit analysis (IACMST, 2004) shows that benefits really start to accrue after 10 years. In 2007 - 2012 exploitation of (i) the time series being acquired, (ii) the model-data synthesis and (iii) the increasingly available quantities of real-time data (e.g. river flows) can be carried out through Sustained Observation Activity (SO) 11, to provide an integrated assessment and short term forecasts of the coastal ocean state.

Overall Aims and Purpose of SO 11

To continue and enlarge the scope of the existing coastal observatory in Liverpool Bay to routinely monitor the northern Irish Sea

To develop the synthesis of measurements and models in the coastal ocean to optimize measurement arrays and forecast products. Driving forward shelf seas' operational oceanography with the direct objective of improving the national forecasting capability, expressed through links to the National Centre for Ocean Forecasting (NCOF)

To exploit the long time-series of observations and model outputs to: a) identify the roles of climate and anthropogenic inputs on the coastal ocean's physical and biological functioning (including impacts of nutrient discharges, offshore renewable energy installations and fishing activity) taking into consideration the importance of events versus mean storms / waves, river discharge / variable salinity stratification / horizontal gradients; b) predict the impacts of climate change scenarios; and c) provide new insights to Irish Sea dynamics for variables either with seasonal cycles and interannual variability, or which show weak or no seasonal cycles

To provide and maintain a 'laboratory' within which a variety of observational and model experiments can be undertaken (Oceans 2025 Themes 3, 6, 8, 9), including capture of extreme events

Demonstrate the value of an integrated approach in assessment and forecasting

Demonstrate the coastal observatory as a tool for marine management strategies through collaboration with the Environment Agency (EA), Department for Environment, Food and Rural Affairs (DEFRA), Joint Nature Conservation Commmittee (JNCC), English Nature (EN), Department of Agriculture and Rural Development (DARD), and Local Authorities, providing management information pertinent to policy (e.g. Water Framework Directive)